Abstract Large carbonate microbialite build-ups are relatively uncommon in ancient fresh-water lacustrine basins as compared with those marine and saline environments. This paper discusses the formation of a large continental lacustrine deposit, the Oligocene-Miocene Carinao Formation in Argentina, which contains large bioherms. The lacustrine formation occur in N-S corridor and is mostly composed by meter scale pinnacles and sheet-like carbonate beds that grade to detrital deposits towards the more subsident southern areas. The main facies are autochthonous and allochthonous limestones and detrital deposits. The autochthonous limestones include the carbonate pinnacles, which are about 4 m high and 0.5 m in diameter and coalesce laterally to form very continuous beds (several kms). The pinnacles are formed by plate-like, dome, vertically elongated and irregular horizontal bioherms, most of them with radial structure. The bioherms are boundstones of fibrous (fans and spherulites) and feather calcite crystals, micrite and inequigranular calcite mosaics. Both biogenic and abiogenic processes interfered in carbonate precipitation. Allochthonous limestones include peloidal, ostracod and intraclastic limestones, some containing coated grains. Polymictic conglomerates and cross-bedded hybrid arenites deposited in a fluvial-deltaic system located at the southwest of the basin. δ13C values vary between −0.4 and − 3.2‰ VPDB and δ18O are comprised between −5.7 and − 8.6‰ VPDB. The 87Sr/86Sr ratios range between 0.7061 and 0.7056. The Carinao Formation deposited in a fresh-water lake, sourced by meteoric and deep-groundwater. Tectonics was a main control determining the configuration of the lake system, the water supply and the alignment of some bioherms. The vertical succession or the different bioherms morphologies reflects well the lake level changes controlled by both tectonic and climate.

中文翻译：

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阿根廷巴塔哥尼亚古近系湖相微生物岩尖峰：相和对照

摘要 与海洋和咸水环境相比，大型碳酸盐微生物岩堆积在古代淡水湖盆中相对少见。本文讨论了大型陆相湖相矿床阿根廷渐新世-中新世 Carinao 组的形成，其中包含大型生物礁。湖相地层发生在 NS 走廊，主要由米级尖峰和片状碳酸盐岩床组成，这些岩层向更沉降的南部地区渐变为碎屑沉积。主要相是本土和外源石灰岩和碎屑沉积。原生石灰岩包括碳酸盐尖峰石，它们高约 4 m，直径约 0.5 m，横向合并形成非常连续的层（数公里）。尖峰由板状、圆顶、垂直拉长和不规则的水平生物礁，大部分呈放射状结构。生物礁是纤维状（扇形和球晶）和羽毛方解石晶体、泥晶和不等粒方解石镶嵌物的边界石。生物和非生物过程都会干扰碳酸盐沉淀。外来灰岩包括球状灰岩、介形灰岩和碎屑灰岩，其中一些含有包覆颗粒。沉积在盆地西南部河流-三角洲系统中的混杂砾岩和交错层状杂化砂岩。δ13​​C 值在 -0.4 和 - 3.2‰ VPDB 之间变化，而 δ18O 包含在 -5.7 和 - 8.6‰ VPDB 之间。87Sr/86Sr 比率范围在 0.7061 和 0.7056 之间。Carinao 组沉积在一个淡水湖中，来源于大气和深层地下水。构造是决定湖泊系统配置、供水和一些生物礁排列的主要控制因素。垂直演替或不同的生物礁形态很好地反映了受构造和气候共同控制的湖泊水位变化。